PF Correction Techniques in highly varying load

Transcription

1 PF Correction Techniques in highly varying load Atul Tare Contents Issues faced in Industries Impact of varying loads on PF - various applications Impact of method of capacitor switching on Harmonics Impact of varying loads on DG sets Regulatory Initiatives Criteria for appropriate PF Improvement mechanism Solution you need

2 Issues Faced in Industries Modernization of Industries Shift to Electronic Controls Almost all loads (which were hitherto linear) became non linear To maximize PF incentives, source side PF improvement is attempted through Fixed capacitors or through APFC or slow response Thyristorized systems. Issues Faced in Industries While this helps maximize PF Incentive, PF under low load, fast changing loads, unbalanced loads is found either low lagging or leading. Improper method of capacitor switching is seen to generate Harmonics. Unbalanced loading conditions are prevailing in the industry.

3 Issues Faced in Industries Equally distributed single phase loads across three phases are not necessarily a balanced load. When one single phase load trips, the load becomes unbalanced, calling for Unbalanced PF compensation. Impact of varying loads on PF - various applications

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9 Aluminum Rolling Mill application Drive application

10 Furnace application Mining application

11 CT Scan application

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13 Unbalanced PF across phases Impact of varying load on PF

14 Impact of varying load on PF Resulting PF dropping to 0.01 lag momentarily When load changes kvar does not change adequately APFC not solution to all loads The load is changing ultra fast and is unbalanced across phases. For the same load levels, the PF profile of individual phases remain unchanged ( with and without APFC) though the load is unbalanced. Average PF is leading with APFC

15 Other Applications High Rise Buildings where many lifts can operate at a time. Furnace Loads Industries where Heavy Motors are switched on simultaneously Industries experiencing Voltage Flickering Problem.

16 Effect of Capacitor switching method on harmonics Without capacitor With capacitor Impact of wrong compensation on harmonics 13.8% THD I step 1 APFC Switched on 14.8% THD I step % THD I step % THD I step % THD I With every step of APFC, PF improves and THD I increases. % THD I increased from 13.8% to 22% on application of 200 kvar Balanced APFC.

17 Impact of wrong compensation on harmonics APFC Switched on 5.12% THD V step % THD V step 2 step % THD V 6.24% THD V step % THD V With every step of APFC, PF improves and THD V also increases. % THD V increased from 5.12% to 6.28 % on application of 200 kvar Balanced APFC. Effects of Harmonics High harmonics results in: - Cable overheating in undersized cables - Cable line loss in oversized cables - Nuisance tripping of Breakers - Resonance blow up of Capacitors. - Damage to Power Transformer - Malfunctioning of Electronic Controls and devices

18 SOURCE AND LOAD SHOULD WORK IN HARMONY. Load EB/DG EB/DG Load.POWER QUALITY ASSESSMENT AND CORRECTION ENSURES THIS OBJECTIVE. Impacts of varying load on DG sets DG Sets are the most vulnerable to varying loads: - Oversized or undersized DG resulting in high fuel consumption or DG not taking load. - Production loss when DG not taking load - Increased inventory to cope up with power cuts - Poor Quality of products especially welding components - increased rejection - Poor Power Factor

19 Regulatory Initiatives Encourage customers to maintain a flat load profile. Bill customers on kvahr instead of kwhr. PF incentive is withdrawn. Consumers above 500 kva contract demand will have to declare Harmonic Levels and their plans to mitigate them. (Position varies from State to State). Criteria - Appropriate PF Improvement solution Rate of Change of Load Capacitor Switching Technique Type of load Balanced or Unbalanced Source Independency DG Compatibility Harmonic Mitigation

20 What do you need? The Solution should provide - Cycle to Cycle Compensation In 20 milliseconds - Transient free switching - Curtailing harmonics to desired levels - Compatible to run on both DG and EB supply - Maintain Unity Power Factor under Unbalanced loading conditions Cummins can help you with a System having features Cycle-by-cycle reactive power compensation providing mirror image compensation Transient-Free Solid-state Capacitors Switching Energy Savings Compatible to both EB and DG Enhancement of generation capacity (DG Sets) Harmonic Filtration Prevention of Voltage drops, Reduction of Voltage Flickering Comprehensive Power Quality Analyzer Self testing and comprehensive reporting feature

21 Thank You Contact Us: Atul Tare Power Electronics Cummins India Ltd Mob: